•Editorial note: An earlier version of this story suggested that the Network Rail document had been adopted as current policy. This article has been amended to reflect Network Rail’s assertion that the document contains policy options none of which have been adopted.

Network Rail has drawn up a plan to target all “leaf fall” trees for removal alongside its tracks, according to an internal policy document seen by the Guardian.

The document sets out a series of alternatives for dealing with the millions of trees along Britain’s railway over the next five years, and says the preferred option is a programme of “enhanced clearance”.

[Network Rail says the document is hypothetical modelling and that it has no plans to implement the favoured option presented in the document. It says that it cuts down about 1,000 trees a week at present, and has no plans to change that.]

After discussions with Network Rail, Jo Johnson, the rail minister, set up a review into vegetation management . He called for all tree felling to be suspended during the current nesting season - March to August.

Johnson said: “This review will look at all aspects of this issue, including, for instance, whether Network Rail has the capacity and capability to control vegetation in a way that minimises harm to wildlife, and whether staff need more training to help with tree identification and identifying approaches that would be better than felling.”

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The leaked document seen by the Guardian sets out a new policy option which appears to go further than any current environmental management. It would involve an “enhanced level of clearance” of trees and vegetation from the railway banks along 20,000 miles of lines in the UK, in an attempt to deal with costly delays to services and improve safety.

Network Rail says it owns 6m trees. Its internal document identifies 13 million trees within falling distance of the tracks – some on third party land and some on its own land. “Network Rail is responsible for any damage that they may cause unless it can be robustly demonstrated that it has taken reasonable steps to reduce the risk of that damage occurring,” the document states.

Network Rail said in a statement that it was constantly balancing the needs of the environment against passenger health and safety.

But it denied the document was a statement of intention, describing it as “a piece of modelling work” that has not been adopted as policy.

“It is a piece of modelling work our regulator asked us to do that actually demonstrates [that] moving to a more aggressive vegetation approach is very costly and does not represent value for money,” a spokesman said in an email to the Guardian.

The document specifies that it would need £41,000 per mile of track for the enhanced clearance. It said this would result in “a far better performing safer railway.”

If the estimate is extrapolated across the entire 20,000-mile network, it would cost more than £800m.

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The document says that certain species of trees pose greater risk due to the amount and size of leaves they produce. They include sycamore, poplar, horse and sweet chestnut, ash and lime.

Network Rail says in the document that it needs to reduce the risk of leaves and trees falling on to the lines, improve performance and safety and cut the hundreds of millions of pounds it pays in compensation – called schedule 8 payments – for delays.

Entitled Lineside Asset Management Control Period 6 (CP6), the document’s preferred option involves the “removal of all leaf fall species” within falling distance of the track, “intensive intervention” on vegetation in close proximity to the railway and the removal of emergent lower level growth at the earliest stage.

The area for management of scrub, grasses, trees and shrubs will also increase from five metres either side of the railway – which has been the policy for the last five years – to a minimum of 6.5m.

Grasses and scrubland alongside Britain’s railway lines are made up of more than 1,600 species of plants, including 900 varieties known of as “railway species” that are exclusive to the trackside.

Gove invited Mark Carne, chief executive of Network Rail, for talks at his office on Wednesday.

Network Rail says it cuts down about 50,000 trees a year. It has not responded to requests to provide the Guardian with an aerial map highlighting “problem” trees earmarked for felling.

A freedom of information response revealed that 30,000 trees were felled by Network Rail or their contractors on the west coast mainline between Euston and Carlisle in the 12 months between February 2016 and February 2017. Network Rail said there were no plans to replace any of the trees in its FOI response.

Network Rail says in the document it will adhere to environmental legislation which requires it to restrict practices at certain locations or certain times of the year. It says the risks to poor performance and safety from trees includes obstruction of the line, causing delays and putting staff and passengers at risk.

Between March 2016 and March 2017 there were 720 incidents with trees, according to the document. Of these 233 trees were struck by trains. “The likelihood of a tree failure causing an accident is high,” the document states.

The company says the impact from falling leaves in the autumn of 2015 involved four signals passed at danger, 91 wrong side failures and 61 station overruns due to poor rail adhesion attributed to leaf fall contamination.

These incidents, it says, cost Network Rail between £100m and £150m.

Network Rail says in the document that trees and vegetation can have a positive benefit in terms of lineside ecology where desirable flora and fauna have been identified and sustainable management plans have been put into place. It also states the company will “manage the vegetation to comply with legal requirements to protect the environment.”

A spokesperson for Network Rail said: “Last year we recorded over 400 incidents of trains colliding with fallen trees and another 1,000 where they caused delays to services, costing the industry over £100m. As a result, we have well thought-out standards and policies in place that have been developed over many years with the help of experts that we believe strike the right balance and maintains a safe and biodiverse line side.

“Most of the time when putting those standards and policies into action we get it right, but sometimes we don’t.”

Sara Lom, chief executive of the Tree Council, which works closely with Network Rail, has not seen the new policy document. She said: “We are Network Rail’s critical friend. When things go wrong, as they sometimes do, we tell them.”

She said the charity was carrying out trials with the company this autumn to look at different ways to manage vegetation apart from tree felling. “Alternatives to removal could be coppicing or pollarding or hedging,” she said. “That is better for wildlife, and better for people in the local community.”

• This article was amended on 24 August 2018 following a complaint from Network Rail. The readers’ editor substantially upheld the complaint, finding that in initial reports the status of the leaked policy options document had been overstated.